Editing Complementary DNA (section)

{{Short description|DNA reverse transcribed from RNA}}
{{Redirect|CDNA|other uses|CDNA (disambiguation)}}
{{About||the general property of complementarity in molecular biology|Complementarity (molecular biology)|complementation tests used in genetics research|Complementation (genetics)}}
{{Use dmy dates|date=May 2020}}
{{more citations needed|date=October 2010}}

[[File:Cdnaarray.jpg|thumb|right|250px|Output from a '''cDNA''' [[DNA microarray|microarray]] used in testing]]

In [[genetics]], '''complementary DNA''' ('''cDNA''') is [[DNA]] that was reverse transcribed (via [[reverse transcriptase]]) from an RNA (e.g., [[messenger RNA]] or [[microRNA]]). cDNA exists in both [[ssDNA|single-stranded]] and double-stranded forms and in both natural and engineered forms.

In engineered forms, it often is a copy (replicate) of the naturally occurring DNA from any particular organism's natural genome; the organism's own mRNA was naturally transcribed from its DNA, and the cDNA is reverse transcribed from the mRNA, yielding a duplicate of the original DNA. Engineered cDNA is often used to [[gene expression|express]] a specific [[protein]] in a cell that does not normally express that protein (i.e., [[heterologous]] expression), or to sequence or quantify mRNA molecules using DNA based methods (qPCR, RNA-seq). cDNA that codes for a specific protein can be transferred to a recipient cell for expression as part of [[recombinant DNA]], often bacterial or yeast expression systems.<ref>{{Citation |last=Hastings |first=P. J. |title=Complementary DNA (cDNA) |date=2001-01-01 |pages=433 |editor-last=Brenner |editor-first=Sydney |editor-last2=Miller |editor-first2=Jefferey H. |url=https://www.sciencedirect.com/science/article/pii/B0122270800002536 |access-date=2022-11-29 |place=New York |publisher=Academic Press |language=en |isbn=978-0-12-227080-2 |encyclopedia=Encyclopedia of Genetics}}</ref> cDNA is also generated to analyze [[transcriptome|transcriptomic]] profiles in bulk tissue, single cells, or single nuclei in assays such as [[microarray]]s, [[Real-time polymerase chain reaction|qPCR]], and [[RNA-Seq|RNA-seq]].

In natural forms, cDNA is produced by [[retrovirus]]es (such as [[HIV-1]], [[HIV-2]], [[simian immunodeficiency virus]], etc.) and then integrated into the host's genome, where it creates a [[provirus]].<ref name="CroyNotes1998">{{Cite web |last=Croy |first=Ron |title=Molecular Genetics II - Genetic Engineering Course (Supplementary notes) |url=http://dwb4.unl.edu/Chem/CHEM869N/CHEM869NLinks/www.dur.ac.uk/~dbl0www/Staff/Croy/cDNAfigs.htm |archive-url=https://web.archive.org/web/20020824023822/http://www.dur.ac.uk/~dbl0www/Staff/Croy/cDNAfigs.htm |archive-date=24 August 2002 |access-date=4 February 2015 |website=Durham University durham.ac.uk; 20 April 1998}}</ref>

The term ''cDNA'' is also used, typically in a [[bioinformatics]] context, to refer to an mRNA transcript's sequence, expressed as DNA bases (deoxy-GCAT) rather than RNA bases (GCAU).

Patentability of cDNA was a subject of a 2013 [[US Supreme Court]] decision in [[Association for Molecular Pathology v. Myriad Genetics, Inc.]] As a compromise, the Court declared, that [[exons]]-only cDNA is patent-eligible, whereas isolated sequences of naturally occurring [[DNA]] comprising [[introns]] are not.